This document discusses Rickettsia, which are small, Gram-negative bacteria that cause diseases transmitted by arthropod vectors like ticks and fleas. It outlines several Rickettsia species and the diseases they cause including typhus, Rocky Mountain spotted fever, and Q fever. It describes the characteristics of Rickettsia as obligate intracellular parasites that infect endothelial cells. Symptoms and treatment options for various Rickettsial diseases are also summarized.